Feature formation in thick-film inks
In a method for forming one or more features in a thick-film ink deposited on a substrate, a photoimagable material is used to define a negative of the one or more features on the substrate. A thick-film ink is then deposited on at least part of the substrate, abutting at least some of the photoimagable material. The thick-film ink is cured, and the photoimagable material is removed. One embodiment of the method is used to produce a channel plate. Another embodiment of the method is used to produce a switch.
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It is sometimes necessary to form a feature or features in a thick-film ink (or “slurry”) deposited on a substrate. One way to do this is by screen printing the features. With screen printing, a screen having the features formed therein is placed over the substrate, and the thick-film ink is deposited on the substrate through the screen. Another way to form features in a thick-film ink is to stencil print the features. With stencil printing, a stencil having the features formed therein is placed over the substrate, and the thick-film ink is deposited on the substrate through the stencil. While screen printing is typically better suited to the deposition of relatively thinner thick-films, stencil printing typically offers better release characteristics when depositing relatively thicker thick-films. However, each of these processes is limited in the types of features it can be used to produce—especially in a micro or sub-micro environment.
Some of the limiting factors of screen and stencil printing processes include larger than desired feature alignment tolerances, feature width tolerances, and feature thickness tolerances. Larger than desired feature alignment and feature width tolerances can result, for example, from screen and stencil deflection, screen and stencil manufacturing tolerances, screen and stencil instability, slumping of the thick-film ink before and during cure, edge effects at feature edges from the wire mesh of a screen stencil, and nonuniformities in the screen and stencil printing processes as a whole. Larger than desired feature thickness tolerances can result, for example, from wire mesh removal dynamics, thick-film ink slumping and shrinkage, and nonuniformities in the screen and stencil printing processes as a whole.
SUMMARY OF THE INVENTIONOne aspect of the invention is embodied in a method for forming one or more features in a thick-film ink deposited on a substrate. As part of the method, a photoimagable material is used to define a negative of the one or more features on the substrate. A thick-film ink is then deposited on at least part of the substrate, abutting at least some of the photoimagable material. Thereafter, the thick-film ink is cured, and the photoimagable material is removed.
Another aspect of the invention is embodied in a channel plate. The channel plate is produced by using a photoimagable material to define a negative of one or more channels on a substrate, and then depositing a thick-film ink on at least part of the substrate, abutting at least some of the photoimagable material. Thereafter, the thick-film ink is cured, and the photoimagable material is removed to form the one or more channels.
Yet another aspect of the invention is embodied in a switch. The switch is produced by using a photoimagable material to define a negative of one or more channels on a substrate, and then depositing a thick-film ink on at least part of the substrate, abutting at least some of the photoimagable material. Thereafter, the thick-film ink is cured, and the photoimagable material is removed to create a channel plate. The one or more channels in the channel plate are then aligned with at least one feature on a substrate, and at least a switching fluid is sealed between the channel plate and the substrate.
Other embodiments of the invention are also disclosed.
Illustrative embodiments of the invention are illustrated in the drawings, in which:
According to
If necessary, the photoimagable material may be cured before or after various stages of the above process. For example, the photoimagable material may be partially or fully cured prior to patterning, subsequent to patterning, or subsequent to developing. Curing may be achieved by exposing the photoimagable material to ambient conditions for a period of time, by heating the photoimagable material, by submersing the photoimagable material in an appropriate solution, or by other means.
By way of example, the photoimagable material may be a dry film or viscous liquid. These materials may be patterned with a fine granularity, thereby enabling the precise location of feature edges, and allowing smaller features to be defined. Dry films also provide for very good thickness control.
Following use of the photoimagable material to define feature negatives, a thick-film ink is deposited 104 on at least part of the substrate, abutting at least some of the photoimagable material. See
The thick-film ink may be deposited in a variety of ways. For example, the thick-film ink may be deposited by means of spin-coating, curtain-coating, stencil printing, screen printing, or doctor blading. Some deposition processes may result in the thick-film ink having a depth that is equal to (or possibly even less than) the depth of the photoimagable material. Other deposition processes may result in the thick-film ink having a depth that is greater than the depth of the photoimagable material. In fact, the thick-film ink may even cover the photoimagable material. If this is the case, chemical-mechanical planarization, grinding, lapping, polishing, or other means may be used to adjust the thickness of the thick-film ink (possibly removing some of the photoimagable material in the process).
By way of example, the thick-film ink may be a glass, ceramic, or polymer-based thick film.
Following deposition of the thick-film ink, the thick-film ink is cured 106, and the photoimagable material is removed 108 (
In some cases, curing the thick-film ink may only comprise drying the thick-film ink (e.g., by exposing it to ambient conditions or heating it for a period of time), or submersing the photoimagable material in an appropriate solution. However, in most cases, curing the thick-film ink will comprise firing the thick-film ink at a high temperature.
Methods for removing the photoimagable material include developing, etching, or burnout. The latter can be used, for example, when the composition of the photoimagable material is such that it will combust or vaporize as the thick-film ink is fired.
Optionally, the thickness of the thick-film ink may be adjusted by removing a portion of the thick-film ink subsequent to curing the thick-film ink. This may be accomplished by means of chemical-mechanical planarization, grinding, lapping, or polishing, for example.
If desired, the method 100 may be repeated to form another feature (or set of features) in another thick-film ink that is deposited on top of the existing thick-film ink. In this manner, it is possible to form exceptionally deep features, or features with non-constant characteristics in the thickness direction. For example, features could be formed in thick-film layers of differing thickness, or features could be formed in thick-film layers having different compositions.
Additional thick-film ink feature layers may also be formed by repeating FIG. 1's defining, depositing and curing steps prior to removal of the first-applied photoimagable material.
The
The channel plate 900 may be used in the manufacture of fluid-based switches such as liquid metal micro switches (LIMMS).
In one embodiment of the switch 1000, the forces applied to the switching fluid 1016 result from pressure changes in the actuating fluid 1018. The pressure changes in the actuating fluid 1018 impart pressure changes to the switching fluid 1016, and thereby cause the switching fluid 1016 to change form, move, part, etc. In
By way of example, pressure changes in the actuating fluid 1018 may be achieved by means of heating the actuating fluid 1018, or by means of piezoelectric pumping. The former is described in U.S. Pat. No. 6,323,447 of Kondoh et al. entitled “Electrical Contact Breaker Switch, Integrated Electrical Contact Breaker Switch, and Electrical Contact Switching Method”. The latter is described in U.S. patent application Ser. No. 10/137,691 of Marvin Glenn Wong filed May 2, 2002 and entitled “A Piezoelectrically Actuated Liquid Metal Switch”. Although the above referenced patent and patent application disclose the movement of a switching fluid by means of dual push/pull actuating fluid cavities, a single push/pull actuating fluid cavity might suffice if significant enough push/pull pressure changes could be imparted to a switching fluid from such a cavity. In such an arrangement, the channel plate for the switch could be constructed similarly to the channel plate 900 disclosed herein.
The channel plate 900 of the switch 1000 may have a plurality of channels 902–910 formed therein, as illustrated in
A second channel or channels 902, 910 may be formed in the channel plate 900 so as to define at least a portion of the one or more cavities 1004, 1008 that hold the actuating fluid 1018. By way of example, these actuating fluid channels 902, 910 may each have a width of about 350 microns, a length of about 1400 microns, and a depth of about 300 microns.
A third channel or channels 904, 908 may be formed in the channel plate 900 so as to define at least a portion of one or more cavities that connect the cavities 1004–1008 holding the switching and actuating fluids 1016, 1018. By way of example, the channels 904, 908 that connect the actuating fluid channels 902, 910 to the switching fluid channel 906 may each have a width of about 100 microns, a length of about 600 microns, and a depth of about 130 microns.
The one or more channels 902–910 in the channel plate 900 may be aligned with one or more features on the substrate 1002, and the channel plate 900 may then be sealed to the substrate 1002, by means of an adhesive or gasket material, for example. One suitable adhesive is Cytop™ (manufactured by Asahi Glass Co., Ltd. of Tokyo, Japan). Cytop™ comes with two different adhesion promoter packages, depending on the application. When a channel plate 900 has an inorganic composition, Cytop™'s inorganic adhesion promoters should be used. Similarly, when a channel plate 900 has an organic composition, Cytop™'s organic adhesion promoters should be used.
Optionally, and as illustrated in
Additional details concerning the construction and operation of a switch such as that which is illustrated in
Forces may be applied to the switching and actuating fluids 1316, 1318 in the same manner that they are applied to the switching and actuating fluids 1016, 1018 in
The channel plate 900 of the switch 1300 may have a plurality of channels 902–910 formed therein, as illustrated in
A second channel or channels 902, 910 may be formed in the channel plate 900 so as to define at least a portion of the one or more cavities 1304, 1308 that hold the actuating fluid 1318.
A third channel or channels 904, 908 may be formed in the channel plate 900 so as to define at least a portion of one or more cavities that connect the cavities 1304–1308 holding the switching and actuating fluids 1316, 1318.
Additional details concerning the construction and operation of a switch such as that which is illustrated in
The use of channel plates is not limited to the switches 1000, 1300 disclosed in
While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.
Claims
1. A method for forming a switch, comprising:
- a) using a photoimagable material to define negatives of one or more channels on a substrate;
- b) depositing a thick-film ink on at least part of the substrate, abutting at least some of the photoimagable material;
- c) curing the thick-film ink;
- d) removing the photoimagable material to create a channel plate; and
- e) aligning the one or more channels in the channel plate with at least one feature on a substrate, and sealing at least a switching fluid between the channel plate and the substrate.
2. The method of claim 1, wherein using the photoimagable material to define a negative of the one or more channels, comprises:
- a) depositing the photoimagable material on the substrate;
- b) patterning the negative of the one or more channels in the photoimagable material; and
- c) removing unwanted portions of the photoimagable material.
3. The method of claim 1, wherein the photoimagable material is deposited as a dry film.
4. The method of claim 1, wherein the photoimagable material is deposited as a liquid.
5. The method of claim 1, wherein the thick-film ink is deposited by means of spin-coating.
6. The method of claim 1, wherein the thick-film ink is deposited by means of curtain-coating.
7. The method of claim 1, wherein the thick-film ink is deposited by means of doctor blading.
8. The method of claim 1, wherein the thick-film ink is deposited by means of screen printing.
9. The method of claim 1, wherein the thick-film ink is deposited by means of stencil printing.
10. The method of claim 1, wherein curing the thick-film ink comprises drying the thick-film ink.
11. The method of claim 1, wherein curing the thick-film ink comprises firing the thick-film ink.
12. The method of claim 1, wherein the photoimagable material is removed prior to said curing.
13. The method of claim 1, wherein the photoimagable material is removed during said curing.
14. The method of claim 1, wherein the photoimagable material is removed after said curing.
15. The method of claim 1, further comprising, adjusting a thickness of the thick-film ink, subsequent to curing the thick-film ink, by removing a portion of the thick-film ink.
16. The method of claim 1, further comprising, repeating said defining, depositing, curing and removing actions to form another channel in another thick-film ink that is deposited on top of the existing thick-film ink.
17. The method of claim 1, further comprising, prior to removing the photoimagable material, repeating said defining, depositing and curing actions to form another channel in another thick-film ink that is deposited on top of the existing thick-film ink.
18. The method of claim 1, further comprising:
- depositing a plurality of electrodes in the one or more channels on the substrate; and
- depositing the switching fluid on the electrodes.
19. The method of claim, further comprising:
- depositing a plurality of wettable pads in the one or more channels on the substrate; and
- depositing the switching fluid on the wettable pads.
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Type: Grant
Filed: Apr 14, 2003
Date of Patent: Jul 4, 2006
Patent Publication Number: 20040202844
Assignee: Agilent Technologies, Inc. (Palo Alto, CA)
Inventor: Marvin Glenn Wong (Woodland Park, CO)
Primary Examiner: Kathleen Duda
Application Number: 10/413,854
International Classification: G03F 7/00 (20060101);